Karst · Limestone · Ain / Revermont (Pont-d'Ain)

Suran

Suran terrain map
Terrain map

The Suran is a Revermont river — the long limestone scarp that runs down the western edge of the Jura and ends somewhere near the Ain.

Poor · Brown Trout
CDC Emerger · 16-20
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
90% confidence
What moved it
  • LevelDry recentlyNo gauge reading
  • Water temp23.1°C
  • ClarityClear
Today’s fly
CDC Emerger
CDC Emerger16-20
Dead-drift
Conditions on the water
Estimate
Level
Dry recently
No gauge reading
Water temp23.1°C
ClarityClear
Weather33°C
WindW 12 km/h
Pressure1015 hPa
Rain · recent0.0 mm
Rain · ahead10.1 mm

No gauge on this water — readings are regional estimates from weather, not a live gauge.

Water temperature for brown trout
Warm — slow
23°C est.ideal 1016°C
0°14°28°
How to fish it · for brown trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
⛔ Water at 23.1°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey

Hatch predictions

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Evidence
Survey-backed · regionalModerate confidence

Backed by regional invertebrate surveys; no sampling on this exact reach yet.

Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
1
Grayling seasonSeason
1
2
2
2
1
Brown SedgeHatch
2
3
2
Freshwater ShrimpHatch
2
3
3
3
3
3
3
3
3
3
3
2
Blue Winged OliveHatch
2
3
3
3
3
2
Mayfly (Green Drake)Hatch
2
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
Gammarus Scud (Olive)
Gammarus Scud (Olive)
12-16 · Gammarus Scud
Dead-drift, sub-surface
Permits & access
Permit required — see local rules.
  • AAPPMA de l'Ain and local associations share management
  • Some fly-only and no-kill parcours — check locally.
What's coming
Plan ahead
5-day outlook
Water here around 23°C. Nothing cooler within range — carry a thermometer.
About this water

The Suran is a Revermont river — the long limestone scarp that runs down the western edge of the Jura and ends somewhere near the Ain. It's neither quite chalk stream nor quite freestone, which gives it a character most anglers don't bother trying to pin down. The water is clear, the banks are friendly, the valley is gentle enough to walk without swearing, and the trout are decent wild fish that will come to a well-presented olive without feeling they've been tricked. Hatches are predictable through the spring — olives, then mayfly in late May, then sedges from June. Summer low water is the main challenge: the Suran can drop to a trickle in a hot August and needs thunderstorm-driven recharge to recover. But pick your window in May or early June and it's one of the most undervalued trout streams in eastern France.

  • Limestone
Water quality (WFD)
  • EcologyModerate
  • ChemicalUnknown

WFD classification · FRDR2015

The full read · show the working · for brown trout · confidence 90%
How the 2 is built — score × weight = contribution
Temperature1 × 28%0.3
Flow60 × 22%13.2
Clarity95 × 18%17.1
Feeding Time60 × 13%7.8
Pressure80 × 7%5.6
Insect activity53 × 12%6.4
Limiting factor: Water temperature (23.1°C) is outside Brown Trout's preferred range (10–16°C)= 50
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitysurvey-backed invertebrate datasurvey
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
  • Trout2nd Saturday of March → 3rd Sunday of September
  • Grayling3rd Saturday of May → 3rd Sunday of September

    France national rule: grayling opens 3rd Saturday of May in all waters. In 1st category (salmonid) rivers, grayling closes with the trout season on the 3rd Sunday of September. Departmental regulations may impose additional restrictions. Always check the relevant département's 2026 arrêté préfectoral.

Related guides
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